CONICET | Buscador de Institutos y Recursos Humanos

Zirconium and its alloys were developed and successfully used as structural materials in nuclear industry. Later, biocompatibility and osseointegration capability in biological fluids was observed, creating interest for its potential use as permanent implants. In biomedical applications, surface characteristics including morphology, electronic nature and crystalline phases present determines the chances for success in service. Anodization constitutes a surface modification route that allows the design of the structure, chemistry and electronic properties of the films formed by carefully selecting process variables. In this work, the surface characterization of pure zirconium and Zr2.5Nb alloy were compared after anodization in a wide potential range in phosphoric acid, in order to compare the films formed and determine the influence of niobium in the structure of the anodic oxide layer. The surface morphology of the specimens was observed by scanning electron microcopy. The crystalline phases were determined by Raman spectroscopy and graze angle X-ray diffraction. Anodic polarization curves and electrochemical impedance spectroscopy tests were performed in borax solution.Semi crystalline zirconium oxides were formed on both materials with monoclinic ZrO2 as the predominant phase. The presence of fissures observed by electronic spectroscopy on anodic films obtained at high potentials was correlated with higher current densities in anodic polarization tests compared with those specimens with no fissures on the anodic films. A double layer structure of the oxide films was determined from electrochemical impedance results, and the film thickness was estimated. Mott-Schottky plots were obtained and the charge carrier density calculated for films growth in different conditions.